This is an archived copy of the Xen.org mailing list, which we have preserved to ensure that existing links to archives are not broken. The live archive, which contains the latest emails, can be found at http://lists.xen.org/
Home Products Support Community News


Re: [Xen-devel] RE: [PATCH] Allocate vmcs pages when system booting

To: "Keir Fraser" <keir.fraser@xxxxxxxxxxxxx>, "Yunhong Jiang" <yunhong.jiang@xxxxxxxxx>
Subject: Re: [Xen-devel] RE: [PATCH] Allocate vmcs pages when system booting
From: "Jan Beulich" <JBeulich@xxxxxxxxxx>
Date: Thu, 18 Mar 2010 10:45:21 +0000
Cc: "xen-devel@xxxxxxxxxxxxxxxxxxx" <xen-devel@xxxxxxxxxxxxxxxxxxx>
Delivery-date: Thu, 18 Mar 2010 03:46:04 -0700
Envelope-to: www-data@xxxxxxxxxxxxxxxxxxx
In-reply-to: <C775F48B.66D1%keir.fraser@xxxxxxxxxxxxx>
List-help: <mailto:xen-devel-request@lists.xensource.com?subject=help>
List-id: Xen developer discussion <xen-devel.lists.xensource.com>
List-post: <mailto:xen-devel@lists.xensource.com>
List-subscribe: <http://lists.xensource.com/mailman/listinfo/xen-devel>, <mailto:xen-devel-request@lists.xensource.com?subject=subscribe>
List-unsubscribe: <http://lists.xensource.com/mailman/listinfo/xen-devel>, <mailto:xen-devel-request@lists.xensource.com?subject=unsubscribe>
References: <4B5043B8020000780002A2E9@xxxxxxxxxxxxxxxxxx> <C775F48B.66D1%keir.fraser@xxxxxxxxxxxxx>
Sender: xen-devel-bounces@xxxxxxxxxxxxxxxxxxx
>>> Keir Fraser <keir.fraser@xxxxxxxxxxxxx> 15.01.10 11:31 >>>
>On 15/01/2010 09:30, "Jan Beulich" <JBeulich@xxxxxxxxxx> wrote:
>>>>> "Jiang, Yunhong" <yunhong.jiang@xxxxxxxxx> 15.01.10 10:06 >>>
>>> b) Can we still turn to the original patch, i.e. pre-allocate all VMCS pages
>>> for all possible CPU?
>> I'm generally opposed to pre-allocations, at least as long as all CPUs are
>> considered 'possible'. Building with a relatively high nr_cpus= setting
>> and then running on a relatively small system results in (close to)
>> unacceptable overhead.
>> In fact it's really not clear to me why cpu_possible_map must be set to
>> CPU_MASK_ALL - if Linux has ways to avoid this, Xen should have too.
>Does Linux manage a good reliable job of cutting down cpu_possible_map? That
>would save cpu_possible_map in my eyes, if we could do that. Otherwise it is
>indeed pretty useless now. Either way, I'd like cpu hotplug notifier chains
>in the 4.1 development window.

Only now got to look into this: Linux simply counts the disabled CPUs
along with the present ones, plus it allows a command line override to
the number of CPU slots reserved for hotplug. I just put together
something similar, partly copying code over from there. Will submit


Xen-devel mailing list

<Prev in Thread] Current Thread [Next in Thread>